The use of hydraulic or other fluid for the transfer of energy from one point to another in a system has been developed to a great extent. It has been found that the principle of plural piston or plunger devices, in which the plungers cooperate with a wobble or swash plate, provides for relatively high efficiency in such devices. Typically, however, the valving incorporated with such devices comprises either a rotary valve adjacent the ends of the plunger cylinders opposite the swash plate, or poppet valves and their accompanying relative complexity.
Such valving has generally been required heretofore, due to the lack of a mechanism providing for fluid transfer directly from the sides of the cylinders. While ported or apertured plungers have been known, the means to provide the precise rotation of the plungers in order to eliminate the need for other types of valve mechanisms has been lacking in the art with the exception of one patent to be discussed below. Moreover, the various related devices fail to take advantage of the gains to be made by more efficient inlet and outlet passages, as well as other improvements.
The need arises for a fluid transfer device which includes inlet and outlet manifolds one of which is contained wholly within the boundaries of the other, and which may take advantage of the efficiencies thus provided. Such a device should also provide for other improvements in the field, such as mechanical means providing for the simultaneous rotation and reciprocation of the plungers and the resulting simplification of the valve mechanism; an integral pressure relief or bypass means; and an integral and simplified means providing for lubrication, cooling and leakage control from the cylinders and plungers.